dredged up from the Gulf of Manaar . 141 



fig. 5) ; but the characteristic acerate flesh-spicule (viz. micro- 

 spined and centrally inflated) is absent, although the spini- 

 spirula is not, but abundantly present. 



The chief interest, however, of this specimen is in the 

 annulated quadriradiate form, on account of its resemblance to 

 the fossil spicule from the Upper Greensand of Haldon Hill, 

 near Exeter, which I represented in 1874 (' Annals,' vol. vii. 

 pi. ix. figs. 44, 45), as it may not only throw some light on 

 the nature of the sponge which bore this, but also on the other 

 moniliform spicules so common in the cavities of the chalk- 

 flints of Oxfordshire and perhaps elsewhere, but first repre- 

 sented from some Irish specimens by Mr. Joseph Wright, 

 F.G.S.,in the Belfast Nat. Hist. Field-Club Report for 1873- 

 74 (pi. ii. figs. 4, 5). 



Tisiphonia penetrans , n. sp. (provisional). 

 (PI. VII. fig. 44, a-d.) 



Amorphous, taking the form of the excavation of the Melo- 

 besian nodule in which it may be growing. Colour white. 

 Spicules of three forms, viz. : — 1, acerate, curved, smooth, 

 fusiform, 27 by l-1800ths (PI. VII. fig. 44, a) ; 2, the same 

 form, but much smaller, 6-1800ths long (fig. 44, b) • 3, stellate 

 flesh-spicule, variable in the number and position of its rays, 

 often quadriradiate, rays microspined, 4-6000ths in diameter 

 (fig. 44, c, d). Size varying with that of the excavated cavity 

 in which it may be growing. 



Hab. Marine. In excavations previously made by litho- 

 domous sponges. 



Loc. Gulf of Manaar. 



Obs. There is still less in this to identify directly with the 

 spiculation of Tisiphonia than in the foregoing species ; but 

 the fades here also strikes me as being allied to this genus. 

 Although found in the excavated cavities of the Melobesian 

 nodule, I doubt if it made the cavities itself; for they often 

 contain a heterogeneous mixture of different forms of spicules 

 which come from as many different kinds of sponges that in 

 my examinations I have never met with, some of which are 

 extremely beautiful and not less remarkable, ex. gr. figs. 29, 

 30 (PI. V.). They are generally, too, enclosed in a transparent 

 membranous investment, which must be the remains of the 

 living organism that not only gathered them together and 

 enclosed them, but dragged them into some of the minutest 

 channels of the excavation in the nodule. What was the 

 nature of that organism, Foraminiferal or Spongious, future 

 observation may determine. 



